US1994161A - Molding machine - Google Patents

Description

March 12, 1935. M w, ZEMAN MOLDING MACHINE Filled July'so. 1952 J VJ lll/1 INVENTOR. 772292 for: fz'mdn @da Patented Mar. 12, 1935 UNITED STATES PATENT' OFFICE MOLDING IMACHINEl Application July 30, 1932, Serial No. 626,269

6 Claims.

This invention pertains to a method of making molds and to mechanism by which the method may be applied. The invention is directed to the production of hard firm molds of even texture,

avoiding irregular density in the molding sand, soft spots, and so on. A mechanism for carrying out the method includes means for placing a pressure on the molding sand which is never released during the jolting operation, but which 0 may be either maintained constant or increased while the jolting is in progress, so that as the sand packs and settles with the jolting the squeeze action is coordinated. Thus the method may be broadly described as a series of concurrent pressure and jolting operations in cycles which may or may not include increasing squeeze pressures. To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particmarly pointed out in the claims.

The annexed drawing and the following description set forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

In the accompanying drawing Fig. 1 is a vertical section through a simple commercial type of machine combined with a diagrammatic elevation of an operation system therefor. The top part of the machine proper in Fig. 1 is taken on the line 11 and the bottom part on line lat-1a, Fig. 2. Fig. 2 is a plan view of the machine shown in Fig. 1, omitting the hydraulic system.

In the usual practice of jolting followed by squeezing, much of the effect of the jolting is lost before the squeeze isapplied, due to a certain elasticity or springingetfect caused by the air entrained in the sand. Th'e present demand is for much harder and more uniform molds than have previously been used, and an attempt has been made to satisfy this by increasing the squeeze pressures, but simply giving a heavy squeeze pressure and holding it does not overcome the springing of the sand, just mentioned, for the reason that it is the jolting rather than the squeezing that works out this entrained air. Although high squeeze pressures are used in the present invention, merely increasing the pressure of the squeezing which follows jolting is unsuccessful to make a hard uniform mold, for the further reason that it compacts the sand between the squeeze head and those portions of the pattern which are near the surface more than the deeper parts of the mold, thus leaving the mold softer at the sides of the pattern.

In general, jolting tends to compact the mold from the bottom, and squeezing to compact it from the top, and the known method of jolting 5 followed by squeezing tends to leave intermediate soft areas. It is to overcome both these objectionable tendencies that the present method of jolting and squeezing simultaneously has been worked out.

In working out mechanism to apply this method it has been borne in mind that the ordinary foundry is supplied with only one pressure system, namely, the compressed air for the jolt and squeeze, which is usually on the order of from 50 to 80 pounds to the square inch. A separate system for high pressure squeezing would be expensive, nor would it be economical to use high pressure air throughout the foundry and step it down for jolting, because the expense of such an installation rapidly increases as the pressure goes up, on account of the necessity of heavier lines, heavier fittings, packing diiculties, etc., not to mention the fact that it is of course simpler to be able to utilize existing air installations.

'I'he preferred form 4of lmechanism illustrated in somewhat diagrammatic and elementary style in Figs. l and 2 is intended to be used with the present compressed air systems, although the invention does not exclude the use of other power means. As best seen in Fig. 1, the mechanism comprises a jolt table 11 movable by the usual type of jolt cylinder 8 and carrying a yoke 12 from one side of which a heavy post or standard 13 rises, supporting a head 14 adapted to swing about this post either to a position over the jolt table or to clear the jolt table. 'I'he head 14 is vertically positioned on the standard between a shoulder 15 and a nut 16. Another post 17 rises from the opposite corner of the yoke 12 and carries at its top means such as nuts 18 which, in combination with the upper part of the post 17, hold a heavy hook or latch 19 on the head 14, by which, when the head is swung into position over the jolt table, it is held against upward displacement. In other words, the members 13 and 17 and their associated parts fasten the head 14 into a unitary structure with the jolt table 11. 'Ihus the jolt table 11, the yoke 12, the posts 13 and 17, and the head 14, with all its associated mechanism, hereafter described, all participate in the jolting movement. 1

Considering the head 14 in more detail, it carries a squeeze head 25 on the lower end of a r squeeze piston 26. Hydraulic pressure, as will be described later, forces the piston 26 downward..

thus squeezing the sand in the flask 27 during the jolting. Air pistons 28 are provided as a convenient means to lift the squeeze head 25 after pressure on the piston 26 has been relieved.

In Figs. 1 and 2 an upward drawing arrangement suitable for use with the invention, but not forming a. part of the invention, is illustrated. The flask 27 surrounding the pattern 30 rests upon a draw frame 31 shown with a stripping plate 31', as usual with cope flasks. Recesses 32 in the edge of the table allow the ends of a pair of arms 33 to fit under the draw frame 31. 'Ihese arms are actuated by draw pistons 34 which may be of the type shown in Patent No. 1,851,321 to Earl F. Oyster, issued March 26, 1932.- Any other suitable drawing means could be used.

'I'he squeeze piston 26 may be connected to the high pressure system by any suitable means such as a pipe 40, having a flexible section 41 to permit the jolting movement and to allow swinging of the head 14. In practice hydraulic pressure, using oil as the liquid medium, is the most satisfactory for the high pressure system, which is therefore so illustrated and described.

An example of a. convenient and suitable high pressure system is shown in diagrammatic style on the left of Fig. 1. It includes a high pressure oil tank 42, a no-pressure tank or sump 43, a pump 44, and various valves and pipe connections. The exact arrangement of the various tanks, piping, and other elements will of course be subject to alteration to nt particular situations. A supply pipe 45 leads from this tank through a quick acting inlet valve 46 and a needle valve 47 to the flexible hose 41 and so to the squeeze cylinder. An exhaust pipe 48 takes off from the pipe 45 between the needle valve and the squeeze cylinder. This pipe is controlled by a quick acting exhaust valve 49, and discharges into the no-pressure tank or sump 43. From the tank 43 a pipe 50 leads to a pump 44 connected to the high pressure tank 42 by a pipe 51 through a check valve 52. The pump 44 is operable by any suitable power means, such as compressed air from the foundry service line, electricity, or otherwise.

A simple control arrangement is shown in the drawing by way of example, consisting of an air valve 60 operated by a hand lever 61. Air supplied from the regular foundry line as at 62 is admitted by the valve to three lines 65, 64, 63, leading respectively to the jolt cylinder 8, to the valve 46, and to the valve 49. The line 65 is for direct supply of compressed air power in the usual way to the jolt cylinder 8, while the valves 46 and 49, in the oil system are air operated. It will be understood that the valve system may assume a wide variety of forms. Ihat shown is convenient and well adapted for manual operation, but either electrical or mechanical instead of pneumatic valve control could be used, or an automatic system, such, for example, as shown in U. S. Patent No. 1,801,654, .issued April 21, 1931 to R. A. Blood.

The operation will now be described.

In making the machine ready for operation, the head 14 is swung around its pivot 15, leaving the top of the jolt table clear so that the flask 27 may be placed, filled with sand, and struck off, all in the usual manner.

The head 14 is then swung shut, into the position shown in Figs. 1 and 2, and the operator moves the Valve handle 61 to the left, thus letting the air successively into the lines 63, 64 and 65,

thus, first, closing the valve 49, second, opening the valve 46, and, third, starting the jolting. It is to be remembered that the table 11, standards 13 and 17 and head 14 all participate in the jolting movement.

Before the operation starts, the high pressure tank 42 will contain a supply of oil under not less than the highest pressure that is to be used in the squeeze cylinder. In practice, this tank is constantly maintained under such pressure, asia source of supply always available for either one or several jolt-squeeze machines.

The opening of the valve 46 lets oil at full pressure into the needle valve 47. This needle valve has been previously so set that the application of full pressure from the tank 42 to the piston 26 will occupy a predetermined length of time, preferably, the time that the jolting is to continue. 'I'he needle valve 47 is set to allow an initial quick flow to give suitable initial squeeze pressure, and for allowing a quick flow whenever the pressure behind the squeeze piston 26 falls below the initial pressure. For example, if it is desired to start with pounds squeeze pressure and go up to pounds during 10 seconds of jolting, the valve 47 would be set to allow free flow of oil up to a pressure of 80 pounds and to have a needle effect at pressures above 80 pounds, so regulated as to reach the full 120 pounds in 10 seconds. But if, for example, 2 seconds of jolting (by which time the pressure would be 88 pounds) settled the sand so far that the squeeze head dropped faster than the needle feed of oil, and the pressure behind the piston consequently dropped below 80 pounds, the valve 47 would automatically give a quick delivery of oil to restore the initial 80 pounds pressure.

Under special circumstances it would be possible to have the needle valve full open Vso that the opening of the valve 46 would apply full tank pressure immediately to the piston 26, but the gradual application of pressure, increasing during the continuance of the jolting, is the method of operation ordinarily employed.

The operator may either count the number of jolt strokes and shut olf the valve 60 at the end of the proper number, or he may watch a. pressure gauge 66 and stop the operationwhen the predetermined pressure has been reached. Obviously, an automatic shut-off could be used related to either of these conditions.

When the valve 60 is shut, the supply of jolting air is rst cut off, second, the valve 46 is closed, and third, the valve 49 is opened The opening of the valve 49 releases the pressure above the piston 26. The squeeze head 25 is now raised, by the pistons 28 (the admission of air to lift these may conveniently be through the valve 60, although this matter of detail is not shown). The oil behind the piston 26 runs down through the open valve 49 and pipe 48 into the tank 43, from which it is forced by the pump 44 into the tank 42. A check valve 52 prevents loss of pressure from the tank 42. It will be noted that no check valve is needed to prevent escape of presf tion of a battery of machines from a single hydraulic system. It will be apparent that if a battery of machines is used, each machine will need only the valves 46, 47 and 63, and that the tanks 42 and 43, pump 44, and the connecting pipes, could be common to the entire system.

It will be seen from the foregoing that I have invented a method of jolting and squeezing simultaneously whereby the action of each takes place under the infiuence of the other, preferably with a constant increase of squeeze pressure as the jolting proceeds, but not excluding the possibility of a constant squeeze pressure during the jolting where special circumstances make this desirable.

The machine which I have invented for carrying out this method is the most suitable which has so far been developed for that purpose, but the method is capable of being applied by other mechanisms.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

l. Mold making apparatus comprising, in combination, a squeeze mechanism, a jolt table carrying said squeeze mechanism, hydraulic means for operating said squeeze mechanism, said hydraulic means comprising a supply of liquid, a tank containing said liquid and means for applying pressure to said liquid therein, a pipe for conveying liquid from said tank to said squeeze mechanism, a quick-opening valve and a restricted-ilow valve in said pipe, another pipe for discharging liquid from said squeeze mechanism, a receptacle for liquid so discharged and a valve in said discharge pipe, and a common control means for said quick-opening valve and said discharge valve whereby opening of the iirst closes the second and vice-versa, and an air supply control for the jolt table also included in said control means.

2. A method of making molds which comprises concurrently jolting and squeezing with increase of the squeezing pressure during the Jolting operation.

3. A method of making molds which comprises jolting the mold, squeezing the same by hydraulic pressure from a pressure-supply means, increasing saidpressure during said jolting operation, releasing said pressure when a predetermined value has been reached, and retuming the pressure-transmitting medium to said pressure-supply means.

4. Mold making apparatus comprising, in combination, a squeeze mechanism, a jolt table carrying said squeeze mechanism, pressure means for operating the squeeze mechanism, said pressure means including a fluid storage reservoir, a connection from the iiuid storage reservoir to the squeeze mechanism, mechanism for increasing the pressure on said reservoir, a control valve for opening connection from said reservoir to said squeeze mechanism, an exhaust valve from said squeeze mechanism, and coordinated operating means for said valves.

5. Mold making apparatus comprising, in combination, a squeeze mechanism, a jolt table car rying said squeeze mechanism, a uid pressure supply for operating the jolt table, supplementary pressure means for operating the squeeze mechanism, said supplementary pressure means including a device for storing fluid under a pressure equal to that of the jolt table operating pressure, and apparatus for increasing the pressure in said supplementary pressure means during the joltmg.

6. Mold making apparatus comprising, in combination, a squeeze mechanism, a jolt table carrying said squeeze mechanism, a uid pressure supply for operating the jolt table, supplementary pressure means for operating the squeeze mechanism, said supplementary pressure means including a iiuid storage reservoir, a uid compressor connected to said reservoir, valves connecting said reservoir to said squeeze mechanism, one being a needle valve to admit iluid slowly to said squeeze mechanism under predetermined pressure differential and quickly when said differential is exceeded, an exhaust valve from said squeeze mechanism, and a coordinating control between the admission and exhaust valves of said squeeze mechanism.

MERTON W. ZEMAN.

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